Schizophrenia (Component 3)

Question 1

Describe the Characteristics of Schizophrenia (10)

Answer 1

Schizophrenia is a severe mental disorder characterised by disturbances in thought, perception, emotions and behaviour, which can significantly impair a person’s ability to function in daily life. The symptoms are commonly divided into positive symptoms (an excess or distortion of normal functioning) and negative symptoms (a reduction or loss of normal functioning).

According to the DSM-5 diagnostic criteria, symptoms must be present for at least one month, with continuous disturbance lasting at least six months, including deterioration in functioning. For a diagnosis, two or more symptoms must be present, such as delusions, hallucinations, disorganised speech, disorganised or catatonic behaviour, or negative symptoms.

Positive symptoms involve experiences that are added to normal behaviour. One example is hallucinations, which are perceptions without an external stimulus. The most common type is auditory hallucinations, where individuals hear voices that are not actually present. For instance, a person with schizophrenia may hear voices commenting on their behaviour or giving them commands, which can influence how they act in everyday situations.

Another positive symptom is delusions, which are strongly held false beliefs that remain despite contradictory evidence. A common example is persecutory delusions, where the individual believes others are trying to harm or spy on them. For example, a person may believe the government is monitoring their thoughts through hidden devices. Another type is delusions of grandeur, where someone believes they possess special powers or importance.

Negative symptoms involve a loss or reduction of normal functioning. One example is avolition, which refers to a lack of motivation to initiate or persist in goal-directed activities. Individuals may struggle to carry out everyday tasks such as going to work, studying, or maintaining personal hygiene.

Another negative symptom is alogia, meaning poverty of speech. Individuals may give very brief responses in conversation or struggle to produce spontaneous speech, reflecting reduced thought processes.

A further negative symptom is anhedonia, which is the reduced ability to experience pleasure from activities that were previously enjoyable, such as hobbies or socialising with friends. People with schizophrenia may withdraw socially because these activities no longer feel rewarding.

Finally, individuals may show flattened affect, where emotional expression is reduced. For example, a person may speak in a monotone voice, show little facial expression, and appear emotionally unresponsive even in situations that would normally provoke emotion.

Overall, schizophrenia is characterised by a combination of positive symptoms such as hallucinations and delusions, and negative symptoms such as avolition, alogia, anhedonia and flattened affect, with diagnosis based on DSM-5 criteria including symptom duration and functional impairment.

Question 2

Describe one biological explanation for
schizophrenia [10]​

Answer 2

One biological explanation for schizophrenia is the dopamine hypothesis. This proposes that schizophrenia is caused by abnormalities in dopamine neurotransmission.

The original dopamine hypothesis suggested that schizophrenia results from hyperdopaminergia, meaning excessively high levels of dopamine activity in the brain. It was believed that individuals with schizophrenia produce too much dopamine or have an increased number of dopamine receptors, particularly D2 receptors. This overactivity leads to overstimulation of postsynaptic neurons and is associated with positive symptoms such as hallucinations and delusions.

Support for this comes from research involving L-dopa, a drug used to treat Parkinson’s disease. L-dopa increases dopamine levels in the brain, and some patients taking L-dopa develop schizophrenia-like symptoms, suggesting that increased dopamine activity can produce psychotic symptoms. Further support comes from Lindström et al. (1999), who used PET scans to measure dopamine synthesis. They found that individuals with schizophrenia showed increased uptake of L-dopa compared to control participants, indicating elevated dopamine production.

However, the dopamine hypothesis has since been revised. Rather than schizophrenia being caused by too much dopamine throughout the entire brain, it is now understood as dopamine dysregulation in specific neural pathways. The mesolimbic pathway is associated with hyperdopaminergia and is linked to positive symptoms. This pathway runs from the ventral tegmental area to the nucleus accumbens and too much dopamine in this pathway cause overstimulation leading to positive symptoms like hallucinations and delusions. Antipsychotic drugs that reduce dopamine transmission (D2 receptors) target this pathwa, reducing the positive symptoms. In contrast, the mesocortical pathway shows hypodopaminergia, particularly in the prefrontal cortex, which is associated with negative symptoms such as avolition and speech poverty. This pathway runs from the ventral tegmental area to the frontal lobe and not enough dopamine in this pathway leads to negative symptoms of schizophrenia like avolition and anhedonia.